Hello, dear all.
In srt format ( subtitles ) we can have very precision timing for the videos.
Eg: 00:01:01,958 --> 00:01:02,958 ( milliseconds included )
But concerning editing video tasks, it's possible to have such precision?
I mean: can I cut / joining videos with milliseconds precision? Yes, even 1 millisecond accuracy on the video.
If yes, which programs can do it properly? AviDemux or Virtualdub can do it, but not with so accuracy as I intend.
Thanks for your tips.
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If you are cutting a source encoded with x264, then it's going have GOP (Group of Pictures) and so there are a block of frames (150-300 frames usually) that can't be cut without errors. So you have to cut at the ending of one GOP and the start of a new one. Videoredo will do what you want for H.264 by re-encoding a select number of frames and not have to worry about GOPs, but it does not work well with anything unless it's in a .TS or .M2TS.
What are the subtitles meant to adorn? - Videos. Not audio, and not standalone, but to accompany and give added information to the video.
What is the most fundamental, atomic timebase you can get with video? - the Framerate.
If the framerate is 60FPS, that means that each picture (frame) is 1/60th of a second long. Or 0.01666666 seconds. Or 16 2/3 millisecond.
That is the best precision you can get with any video of 60FPS (the only way to get higher precision would be to get higher FPS, and videos with less FPS have less precision). No ifs, ands, or buts.
And though you might have worse precision if you happen to have to be editing longer than All-I-Frame (aka Single GOP) videos while avoiding re-encoding, normally ALL, I repeat A*L*L, video editing apps would have this SAME level of precision with all videos of this framerate. (Obviously, this doesn't count append/join/cut/edit apps that only work non-reencoding at GOPsize>1 level, as that is the reason for using them).
And what you may not realize is that ALL subtitling app can also only give you that same level of precision for that same framerate. Regardless of however many decimal points it likes to give you. They MUST land on the timing of the video frame.
Last edited by Cornucopia; 3rd Jan 2019 at 21:07.
You can actually get cuts at microsecond accuracy by using such as FFprobe to find the frame timestamp, but ONLY on I-frames which are the beginning of each GOP as mentioned by KarMa. Other than that they would have to be re-encoded with programs mentioned by KarMa and Davexnet.
So ... use FFprobe to get timestamps and cut at I-Frames or re-encode.
I use FFMpeg to achieve this all the time...
[Attachment 47720 - Click to enlarge]
As already pointed - you can edit video with frame/field accuracy (depends if video is progressive or not) - framerate is your limitation - i could imagine higher accuracy by joining frame on line boundary or even by pixel boundary but see no point for this... And PTS values are represented with way higher accuracy - for TS PTS clock is 90kHz. ie 11.1uS.